Compensated fluid flow control valve

Abstract

A compensated control valve assembly for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load the controlled pressure level of a pressure reducing valve mechanism handling the fluid flow at negative load pressure is varied upstream of an outflow metering orifice arrangement, positioned at the outlet of the fluid motor, in response to pressure at the inlet of the fluid motor, while maintaining this controlled pressure constant at each specific level. The pressure differential across an inflow metering orifice arrangement, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by a positive load pressure compensating control device.

I claim: 
     
       1. A valve assembly interposed between a fluid motor operable to control positive and negative loads and subjected to positive and negative load pressure, fluid exhaust means including reservoir means and a source of pressure connected to a pump, first valve means operable to selectively interconnect said fluid motor with said exhaust means and said source of pressure, positive load pressure control means between said fluid motor and said pump, negative load pressure control means between said fluid motor and said exhaust means including pressure reducing valve means and fluid outflow metering orifice means, said pressure reducing valve means having throttling member means operable to control the flow of fluid through any specific flow area of said fluid outflow metering orifice means at a relatively constant control pressure upstream of said fluid outflow metering orifice means independent of the magnitude of said negative load pressure, and regulating means responsive to said positive load pressure operable to increase said control pressure upstream of said fluid outflow metering orifice means with increase in said positive load pressure whereby fluid flow through said fluid outflow metering orifice means becomes independent of the magnitude of said negative load pressure and can be increased with the increase in said positive load pressure during control of said negative load. 
     
     
       2. A valve assembly as set forth in claim 1 wherein said throttling member means has throttling slot means positioned upstream of said fluid outflow metering orifice means. 
     
     
       3. A valve assembly as set forth in claim 1 wherein said positive load pressure control means includes fluid inflow metering orifice means. 
     
     
       4. A valve assembly as set forth in claim 3 wherein said regulating means has force generating means responsive to pressure downstream of said fluid inflow metering orifice means. 
     
     
       5. A valve assembly as set forth in claim 3 wherein said regulating means has deactivating means of said pressure reducing valve means when pressure at said fluid inflow metering orifice means reaches a certain predetermined level. 
     
     
       6. A valve assembly as set forth in claim 1 wherein said positive load pressure control means includes fluid inflow metering orifice means and positive load pressure compensating control means upstream of said fluid inflow metering orifice means said compensating control means having throttling means operable to control the pressure differential across said fluid inflow metering orifice means at a relatively constant preselected level. 
     
     
       7. A valve assembly as set forth in claim 6 wherein said positive load pressure compensating control means includes compensation energizing means whereby said compensating control means is maintained in minimum flow throttling position in anticipation of positive load compensating action. 
     
     
       8. A valve assembly as set forth in claim 1 wherein said positive load pressure control means includes fluid inflow metering orifice means and positive load pressure compensating control means upstream of said inflow metering orifice means operable to control bypass flow between said pump and said exhaust means to control the pressure differential across said inflow metering orifice means at a relatively constant preselected level. 
     
     
       9. A valve assembly as set forth in claim 1 wherein said positive load pressure control means includes fluid inflow metering orifice means, and positive load pressure compensating control means upstream of said fluid inflow metering orifice means said compensating control means having fluid throttling slot means between said pump and said fluid motor and bypass throttling means between said fluid pump and a series power circuit said positive load pressure control means operable to control the pressure differential across said fluid inflow metering orifice means at a relatively constant preselected level. 
     
     
       10. A valve assembly as set forth in claim 1 wherein logic means has pressure identifying means operable to identify the presence of said positive load pressure and first transmitting means operable to transmit control signal of said identified positive load pressure to said positive load pressure control means and to said regulating means. 
     
     
       11. A valve assembly as set forth in claim 10 wherein said pump has an output flow control responsive to said positive load pressure and said logic means has second transmitting means operable to transmit control signal of said identified positive load pressure to said output flow control of said pump. 
     
     
       12. A valve assembly as set forth in claim 1 wherein said pressure reducing valve means includes energizing means whereby said pressure reducing valve means is maintained in minimum flow throttling position in anticipation of negative load control action. 
     
     
       13. A valve assembly as set forth in claim 1 wherein said pressure reducing valve means has mounting means on said fluid motor. 
     
     
       14. A valve assembly as set forth in claim 1 wherein said negative load pressure control means includes a fluid bypass means operable to supply fluid flow from said source of pressure to said fluid motor. 
     
     
       15. A valve assembly as set forth in claim 1 wherein said negative load pressure control means has fluid flow blocking means operable to prevent fluid flow from said fluid motor to said fluid exhaust means when said positive load pressure drops below a certain predetermined level. 
     
     
       16. A valve assembly interposed between a fluid motor operable to control positive and negative loads and subjected to positive and negative load pressure, fluid exhaust means including reservoir means and a source of pressure connected to a pump, first valve means operable to selectively interconnect said fluid motor with said exhaust means and said source of pressure, fluid inflow metering orifice means interposed between said fluid motor and said pump, positive load pressure compensating control means upstream of said fluid inflow metering orifice means operable to maintain by fluid throttling a relatively constant pressure differential across said fluid inflow metering orifice means, negative load pressure control means between said fluid motor and said reservoir means including pressure reducing valve means and fluid outflow metering orifice means, said pressure reducing valve means having throttling member means operable to control the flow of fluid through any specific flow area of said fluid outflow metering orifice means at a relatively constant control pressure upstream of said fluid outflow metering orifice means independent of the magnitude of said negative load pressure, and regulating means responsive to said positive load pressure operable to increase said control pressure upstream of said fluid outflow metering orifice means with increase in said positive load pressure whereby during control of negative load a relatively constant pressure differential is maintained across said fluid inflow metering orifice means while the pressure level at said fluid inflow metering orifice means is limited to a certain predetermined level. 
     
     
       17. A valve assembly as set forth in claim 16 wherein said compensating control means includes fluid throttling slot means interposed between said pump and said fluid motor. 
     
     
       18. A valve assembly as set forth in claim 16 wherein said compensating control means includes fluid bypass throttling means interposed between said pump and said reservoir means. 
     
     
       19. A valve assembly as set forth in claim 16 wherein said compensating control means includes fluid throttling slot means interposed between said pump and said fluid motor and bypass throttling means interposed between said pump and a series power circuit. 
     
     
       20. A load responsive valve assembly comprising a compensating control assembly and a first valve means having first and second load chambers connected to a fluid motor operable to control positive and negative loads and subjected to positive and negative load pressure, an inlet chamber of the compensating control assembly connected to a fluid pump, outlet chambers operably connected to reservoir means, and a supply chamber, valve spool means operable to sequentially interconnect said load chambers with said supply chamber and said outlet chambers, fluid inflow metering orifice means on said valve spool means operable to meter fluid flow between said supply chamber and said load chambers, compensating control means interposed between said inlet chamber and said supply chamber operable to maintain a relatively constant pressure differential across said fluid inflow metering orifice means during control of said positive and said negative load, logic means operable to identify the presence of positive load pressure in said load chambers and to transmit a positive load pressure signal to said compensating control means, pressure reducing valve means operable to throttle said negative load pressure from said outlet chambers to a relatively constant control pressure level, fluid outflow metering orifice means interposed between said pressure reducing valve means and said reservoir means, and regulating means of said pressure reducing valve means having force generating means responsive to pressure downstream of said fluid inflow metering orifice means and operable to vary the level of said control pressure while said control pressure is maintained constant by said pressure reducing valve means at each selected level. 
     
     
       21. A load responsive valve assembly as set forth in claim 20 wherein said fluid outflow metering orifice means is positioned on said valve spool means. 
     
     
       22. A load responsive valve assembly as set forth in claim 20 wherein said regulating means has force limiting means operable to limit said pressure downstream of said fluid inflow metering orifice means to a certain maximum pressure level during control of said negative load. 
     
     
       23. A valve assembly as set forth in claim 20 wherein said compensating control means includes fluid throttling slot means interposed between said pump and said fluid motor. 
     
     
       24. A valve assembly as set forth in claim 20 wherein said compensating control means includes fluid bypass throttling means interposed between said pump and said reservoir means. 
     
     
       25. A valve assembly as set forth in claim 20 wherein said compensating control means includes fluid throttling slot means interposed between said pump and said fluid motor and fluid bypass throttling means interposed between said pump and a series power circuit. 
     
     
       26. A valve assembly as set forth in claim 20 wherein said regulating means of said pressure reducing valve means has force generating means responsive to pressure downstream of said fluid inflow metering orifice means. 
     
     
       27. A valve assembly as set forth in claim 26 wherein said force generating means has deactivating means operable to deactivate said pressure reducing valve means when pressure of said positive load pressure signal reaches a certain predetermined level. 
     
     
       28. A load responsive valve assembly as set forth in claim 20 wherein said pressure reducing valve means includes first pressure reducing valve means and second pressure reducing valve means. 
     
     
       29. A load responsive valve assembly as set forth in claim 28 wherein said first pressure reducing valve means is interposed between said outlet chamber and first fluid outflow metering orifice means and said second pressure reducing valve means is interposed between said outlet chamber and second fluid outflow metering orifice means. 
     
     
       30. A load responsive valve assembly as set forth in claim 28 wherein said first and second pressure reducing valve means have throttling member means and spring biasing means interposed between said throttling member means.